The present invention relates to techniques for enhancing the powering of and wireless data collection from arbitrarily oriented high-bandwidth remote sensor devices such as inductively powered implant devices.
For the past three decades, biotelemetry has assisted many researchers and clinicians in obtaining physiological information from both patients and animals. With the development of new electronic, communication, battery, and material technologies, the capabilities of biotelemetry systems have expanded, bringing increased performance in the form of longer implantation times, greater channel counts, smaller sizes, and more robust communication.
For a majority of medical applications using biotelemetry implants, it has sufficed to monitor only a few channels of slowly varying DC levels such as pressure, temperature, ion concentration, etc. or small bandwidth signals with bandwidths typically ranging from 100 Hz to 5 kHz per channel such as EKG, EEG, EMG, etc. To date, however, biotelemetry systems have been unable to provide the throughput necessary for certain applications, such as cardiac mapping or high-bandwidth multichannel neural recording in which channel rates in excess of 1 Mbits/sec are often required, thus mandating large amounts of energy to power the implant. For long term studies, the energy requirement becomes even more prohibitive.
Researchers are currently searching for data collection systems that can maximize usage of developing, high-bandwidth sensor systems. Such sensor systems include flexible plastic substrate-based biosensor arrays for biopotential recording, and silicon-based micro-electrode arrays for neural recording.
Also of interest is the ability to collect physiological information from a variety of locations within a subject. This requires a network of sensors placed throughout a region under study. In cardiac mapping, for example, several electropotential arrays may be required at different ischemic or infarcted areas of a heart in order to simultaneously monitor electrical activity during a cardiac event. A desirable implementation for this network has each sensor as a separate telemeter, thereby eliminating the need to interconnect wires among the sensors. The elimination of these wires significantly reduces overall implant bulk and complexity while facilitating implantation.
A fundamental difficulty in developing a high-bandwidth biotelemetry system pertains to implant power consumption. In contrast to low-bandwidth systems, a high-bandwidth system must transmit many more pulses in a given time-period, thus depleting the power source much faster. In addition, the electronics required to sample, process, and encode the sensor data will also draw more energy as the aggregate bandwidth increases. The increased power demands require the use of larger implant batteries or alternative power sources. A popular widely known alternative to relying exclusively on batteries to power an implant is Inductive Power Transfer (IPT).
Inductive Power Transfer uses an AC-energized coil to create a magnetic field that couples with a receiving coil of an inductively powered device. The induced signal appearing at the output of the inductively powered device coil is then rectified and filtered to create a relatively constant DC power source. The xe2x80x9cloosely-coupled transformerxe2x80x9d link provides a means of eliminating and/or recharging inductively coupled biomedical implant batteries or capacitors. This technique has been used not only for biotelemetry devices, but also for artificial hearts, ventricular assist devices, various forms of neural stimulators, and battery recharging.
What is needed is a system which can accurately target arbitrarily oriented inductively powered devices in order to provide power to, and communicate at high data rates with, the arbitrarily oriented inductively powered devices.
The present invention pertains to a system capable of high-bandwidth communication and omnidirectional power transfer to a network of arbitrarily positioned inductively powered devices. Magnetic Vector Steering (MVS) and Half-Cycle Amplitude Modulation (HCAM) are two novel techniques which enhance the powering and control of multiple inductively powered devices. Together, these techniques enable arbitrarily oriented inductively powered devices to receive power and command/programming/control information in an efficient manner that preserves battery life and transmission time. By directing the aggregate magnetic field, using magnetic vector steering, from a near-orthogonal set of AC-energizing coils, selected inductively powered devices can be powered and/or communicated with at desired times. Communication with individual inductively powered devices can also be enhanced through half-cycle amplitude modulationxe2x80x94a technique that allows bit rate transfers up to twice the energizing frequency. The present invention combines power and data transmission circuitry more effectively than the prior art while also significantly reducing the hardware required of an inductively powered device such as a biomedical implant thereby reducing overall implant bulk.
It is an object of the present invention to provide a system for remotely powering one or more inductively powered devices such that the overall bulk of such devices is significantly reduced.
It is a further object of the present invention to provide a data communication system which can modulate a power carrier, communicating with one or more inductively powered devices, with a serial data stream at upto twice the cycle rate of the power carrier.
It is a still further object of the invention to allow the use of a single frequency channel for both power and data transfer to arbitrarily oriented inductively powered devices.
Some of the objects of the invention having been stated, other objects will become apparent as the description proceeds, when taken in connection with the accompanying drawings described as follows: